Just six years ago, the man who turned the Christian Coalition into such a powerful political force that he was called “God’s right-hand man” was all but written off, tarnished by his ties to the disgraced lobbyist Jack Abramoff, then trounced in his campaign to become Georgia’s lieutenant governor.

But after several years in political purgatory, Mr. Reed has found his way back.

At the Republican convention in Tampa, Fla., he was sought after by party luminaries and afforded the ultimate status accommodation, a room in the same hotel as Mitt Romney. And soon he plans to unleash a sophisticated, microtargeted get-out-the-evangelical-vote operation that he believes could nudge open a margin of victory if Mr. Romney can keep the race close.

The other day, sitting in an office lined with framed photographs from back in the heyday — here with President George W. Bush at a White House Christmas party, there with Pope John Paul II at the Vatican — the preternaturally youthful evangelical operative, 51, propped his black ostrich cowboy boots on a coffee table and made what he admits seems an audacious prediction: that record numbers of socially conservative evangelical Protestants will turn out for the first presidential election in history without a Protestant on the Republican ticket.

“God,” he said with a laugh, “has a sense of humor.”

That may be, but Mr. Reed has a plan. And he has the money to back it up: an estimated $10 million to $12 million from contributors across the Republican spectrum, according to a partial list of donors and people with direct knowledge of his operation.

Three years ago, Mr. Reed formed the Faith and Freedom Coalition and began assembling what he calls the largest-ever database of reliably conservative religious voters. In the coming weeks, he says, each of those 17.1 million registered voters in 15 key states will receive three phone calls and at least three pieces of mail. Seven million of them will get e-mail and text messages. Two million will be visited by one of more than 5,000 volunteers. Over 25 million voter guides will be distributed in 117,000 churches.

White evangelicals are a crucial voting constituency, 26 percent of the 2008 electorate and overwhelmingly Republican in recent presidential cycles, exit polls show. With so few truly undecided voters left, bumping up evangelical turnout in swing states like Colorado, Florida, Iowa, Nevada, North Carolina and Ohio would almost certainly help Mr. Romney.

But the success of Mr. Reed’s turnout-stimulus campaign will hinge on a variety of factors, not least whether those voters so dislike some of President Obama’s policies that they can overcome their mistrust of Mr. Romney’s Mormon faith and reversals on issues like abortion. And in an election dominated by jobs and the economy, it remains an open question whether culture-war hot buttons, like the president’s support for same-sex marriage, will be as potent as in the past.

In 2004, Mr. Reed was an architect of an evangelical turnout apparatus that is credited with helping Mr. Bush win re-election. Then came the Abramoff influence-peddling scandal. Though Mr. Reed was not charged, the work his consulting firm did for Mr. Abramoff’s Indian gambling clients by opposing plans for rivals’ casinos sullied his reputation among Christian conservatives, many of whom oppose gambling. Mr. Reed acknowledges that he used bad judgment.

Clint Austin, a Christian lobbyist who used to work with Mr. Reed, said, “Money and power always find a way to get in the same room, and it’s sometimes hard to resist the allure of that. I want to say this with humility because I’m not his judge, but there were so many causes for concern, and a lot of us felt like he needed to step back and get himself refocused.

“And I think that’s what he’s now done.”

Mr. Reed began by aligning himself with Mr. Romney during the primary campaign against Senator John McCain, the eventual Republican nominee in 2008, said Mr. Reed’s friend Deal W. Hudson, president of the Pennsylvania Catholics Network. Mr. Reed distributed a film, “Amendment 6,” that linked the idea of religious tolerance to evangelicals’ acceptance of Mormonism.

“That movie was a great example of how Ralph works,” said Matt Towery, a Georgia political analyst. “I don’t mean this pejoratively, but he is an opportunist. He finds himself an opportunity and he hits it, and he hits it hard.”

With much of the work once done by party committees and campaigns now outsourced to “super PACs” and other outside groups, Mr. Reed saw another opportunity. In 2008, the Obama campaign won the turnout wars with technology and microtargeting data made available by the growth in online shopping.

The Faith and Freedom Coalition, formed in 2009, is Mr. Reed’s attempt to do the same on the right.

To identify religious voters most likely to vote Republican, the group used 171 data points.

It acquired megachurch membership lists. It mined public records for holders of hunting or boating licenses, and warranty surveys for people who answered yes to the question “Do you read the Bible?” It determined who had downloaded conservative-themed books, like “Going Rogue” by Sarah Palin, onto their e-readers, and whether those people also drove pickup trucks. It drilled down further, looking for married voters with children, preferably owners of homes worth more than $100,000.

Finally, names that overlapped at least a dozen or so data points were overlaid with voting records to yield a database with the addresses and, in many cases, e-mail addresses and cellphone numbers of the more than 17 million faith-centric registered voters — not just evangelical Protestants but also Mass-attending Catholics. The group is also reaching out to nearly two million more people who have never registered to vote.

One measure of the coalition’s potential influence is its contributors, who represent a broader Republican constituency than simply the religious right. The group is not required to disclose its donors, but a partial list was obtained by The New York Times.

For example, one donor, Bernard Marcus, the co-founder of Home Depot, supports abortion rights but wants smaller government. On the other hand, the mutual fund manager Foster Friess is a patron of religious conservative causes and was a leading donor to a super PAC that supported Rick Santorum. Another donor is John M. Templeton Jr., who runs a foundation devoted to pursuing “new insights at the boundary between theology and science.”

In addition to its presidential election turnout campaign, the group plans to focus on two state ballot measures: a proposed constitutional ban on same-sex marriage in Minnesota and an effort to recall an Iowa Supreme Court justice who voted to legalize same-sex marriage in the state.

Mr. Reed and his allies agree that social issues alone will not turn the election.

Same-sex marriage, for instance, “doesn’t raise the temperature of the bulk of the Catholic Mass-going voters,” said Mr. Hudson, adding that while it was still a concern, “attitudes about homosexuals have changed so much over the last several years.”

So the group plans to pair its social message with a broader economic one. The president’s health care overhaul will be depicted as both big government spending and an assault on religious liberty; the law mandates that employees of organizations affiliated with religions, like hospitals, universities and charities, be able to obtain free contraception through their health care plans.

In addition, Mr. Obama’s testy relations with Prime Minister Benjamin Netanyahu of Israel, an important issue for many evangelicals, will be highlighted, said Gary Marx, the Faith and Freedom Coalition’s executive director.

Some Republican operatives doubt Mr. Reed will be able to mobilize a new evangelical army.

Still, one early test was the coalition’s work in the 2009 Virginia governor’s race, where exit polls showed that evangelicals’ share of the electorate had jumped to 34 percent from 28 percent in 2008.

“Ralph’s organization played an incredibly important role,” said Phil Cox, the campaign manager for the Republican winner, Bob McDonnell. “He speaks the language.”

A version of this article appears in print on September 23, 2012, on page A1 of the New York edition with the headline: An Evangelical Back From Exile, Lifting Romney. Order Reprints|Today's Paper|Subscribe